Ganglioside-antibodies produced subsequent to Campylobacter jejuni infection may play a role in the pathogenesis of the neurological disorder Guillain-Barre syndrome (GBS). Since lipopolysaccharides (LPS) of certain C.jejuni serotypes associated with GBS (O:2, O:4, O:19) exhibit structural mimicry of gangliosides in their core oligosaccharides, we investigated antibody and ligand cross-reactivities between gangliosides and LPS of these C.jejuni serotypes, GM1-antibody reacted with O:19 LPS reflecting GM1 mimicry by the O:19 core oligosaccharide, On the other hand, asialoGM1-antibody bound to O:2 and O:19 LPS indicating a shared epitope not dependent on ganglioside mimicry, Serum IgA from GBS patients after C.jejuni infection reacted with gangliosides, predominantly GM1, and LPS of all three serotypes, Cholera toxin (GM1 ligand) recognized O:4 and O:19 LPS, whereas peanut agglutinin (Gal beta 1-3GalNAc ligand) recognized LPS of all three serotypes, thereby confirming structural mimicry, These results suggest that LPS from certain C.jejuni strains may function as cross-reactive antigens for anti-ganglioside B cells.